The present invention generally relates to information signal recording discs, and more particularly to an information signal recording disc which is recorded with a stereoscopic television signal comprising video signals for obtaining stereoscopic pictures and audio signals.
Various recording and reproducing systems have been reduced to practice for playing various recording mediums such as a video disc recorded with a television signal. A picture which is obtained by reproducing the television signal from the video disc is a two-dimensional picture. However, there is recently a demand for a video disc recorded with a stereoscopic video signal so that a stereoscopic picture can be obtained by reproducing the stereoscopic video signal from the video disc.
As stereoscopic television systems for obtaining the stereoscopic picture, there are basically two existing systems. According to a first system, a right-eye video signal which is to be reproduced and viewed by the right eye of the viewer and a left-eye video signal which is to be reproduced and viewed by the left eye of the viewer are simultaneously reproduced and measures are taken so that the viewer can only see a reproduced right-eye picture with his left eye. On the other hand, according to a second system, the right-eye video signal and the left-eye video signal are alternately reproduced in time sequence with a predetermined period and measures are taken so that the viewer can only see the reproduced right-eye picture with his right eye and can only see the reproduced left-eye picture with his left eye. These first and second systems have been known for more than ten years. However, as is well known, a broadcasting according to such stereoscopic television systems has not been started.
The broadcasting according to the above stereoscopic television systems has not been started mainly for the following reasons. Firstly, in order to maintain compatibility with the existing television braodcasting system which transmits information related to the two-dimensional picture, it is necessary to divide a frequency band which is allocated for the existing television broadcasting system into a frequency band for transmitting the right-eye video signal and a frequency band for transmitting the left-eye video signal, for example. However, in this case, a number of channels which can be used in the television broadcasting system becomes substantially reduced by one-half. Secondly, in the case where the frequency bands of the right-eye and left-eye video signals are compressed, the television broadcasting system itself becomes quite different from the existing television broadcasting system and it is difficult to reduce such a different system into practice. Thirdly, in the case of the second system described before according to which the right-eye and left-eye video signals are alternately transmitted in time sequence, there is a problem in that the right-eye and left-eye video signals will be reproduced as a double image on a normal television receiver.
On the other hand, the problem of allocating the channels in the stereoscopic television broadcasting system will not occur when recording the stereoscopic video signal on the video disc. Hence, the stereoscopic television system which is used to record the stereoscopic video signal on the video disc can be selected with a large degree of freedom, and there is certainly a significance in recording the stereoscopic video signal on the video disc.
However, it is desirable that the video disc recorded with the stereoscopic video signal is playable on an existing video disc player and that it is possible to to satisfactorily reproduce the normal two-dimensional picture and the normal sound. In addition, it is desirable that the video disc recorded with the stereoscopic video signal is playable on a video disc player employing the first system described before in which the right-eye and left-eye video signals of a simultaneous stereoscopic video signal are reproduced simultaneously, and that this video disc is also playable on a video disc player employing the second system described before in which the right-eye and left-eye video signals of a sequential stereoscopic video signal are alternately reproduced in time sequence.
Accordingly, an information signal recording disc was previously proposed in a Japanese Patent Application No. 59-137701 in which the applicant is the same as the assignee of the present application. This previously proposed disc is primarily designed so that the existing video disc player can reproduce from the disc the stereoscopic picture and also the normal two-dimensional picture. For this reason, when reproducing from the disc the sequential stereoscopic video signal of the second system, a reproducing element must be shifted from one track turn to another track turn on the disc a large number of times. As a result, there is a problem in that audio signals recorded on the disc may not be reproduced satisfactorily. In other words, even when the forced shift of the reproducing element is performed within a vertical blanking period of the video signal, the signals reproduced from the disc at the instant when the reproducing element is shifted become distorted, and the audio signals reproduced from the disc are distorted every time the reproducing element is shifted.
On the other hand, it is desirable that a stereoscopic picture is reproduced from the video disc when the video disc is played on the video disc player and the reproducing element scans over a scanning locus identical to that at the time of a double-speed quick motion reproducing mode. In this case, it is possible to apply the video disc player for a wide range of use.